Does HRT Reduce Your Risk of Dementia? What the Latest Research Actually Says

HRT can help with hot flushes, night sweats, vaginal dryness and a whole host of other menopause symptoms.

But could it also help protect our brains?

That's the question being asked following a major new UK study involving more than 183,000 postmenopausal women.

The headlines are certainly attention-grabbing.

Women who had used hormone replacement therapy (HRT) for at least a year were found to have a 10% lower risk of developing dementia and a 16% lower risk of developing Alzheimer's disease than women who had never used HRT.

Even more interestingly, the apparent benefit wasn't the same for everyone.

So, does this mean HRT prevents dementia?

Not quite.

But the research adds another fascinating piece to the increasingly complicated puzzle of menopause, oestrogen and women's brain health.

What did the study find?

Researchers from the University of East Anglia and University of Exeter analysed data from 183,450 postmenopausal women taking part in the UK Biobank study.

The women were followed for an average of just over 13 years, during which almost 4,000 cases of dementia were identified.

Researchers compared women who had used HRT for at least one year with women who had never used it.

Overall, HRT use was associated with:

• a 10% lower risk of all forms of dementia

• a 16% lower risk of Alzheimer's disease

But when researchers started looking at different groups of women, things became even more interesting.

Timing appears to matter

One of the most striking findings was that the age at which women started HRT appeared to make a difference.

The strongest association with lower dementia risk was seen among women who started HRT between the ages of 46 and 56.

Starting HRT later did not show the same association.

This adds to an existing theory sometimes referred to as the "window of opportunity" – the idea that the effects of HRT may differ depending upon when treatment begins in relation to menopause.

It doesn't mean you should rush out and start HRT at 46 to prevent dementia.

But it does give researchers another important avenue to investigate.

Women with surgical menopause appeared to benefit particularly strongly

The findings were particularly interesting for women who had experienced surgical menopause – for example, following removal of the ovaries.

In this group, HRT use was associated with around a 26% lower risk of dementia.

The association with Alzheimer's disease was even larger in some analyses.

Why might that be?

Surgical menopause can cause a much more sudden drop in oestrogen than natural menopause.

Researchers are therefore interested in whether replacing some of that lost oestrogen could have longer-term effects on the brain.

Again, though, we're talking about an association rather than proof.

What does oestrogen have to do with our brains anyway?

We tend to think about oestrogen in terms of periods, fertility and menopause.

But oestrogen receptors are found throughout the body – including in the brain.

Oestrogen is involved in processes relating to memory, cognition and brain function.

That might help explain something many of us notice during perimenopause:

brain fog.

Forgetting someone's name halfway through introducing them.

Walking upstairs and having absolutely no idea why.

Searching for your phone while you're holding it.

Losing a perfectly ordinary word halfway through a sentence.

These experiences don't mean you're developing dementia. Brain fog and memory difficulties are commonly reported during perimenopause and menopause.

But scientists are increasingly interested in what changing hormone levels might mean for women's brains over the much longer term.

What about the Alzheimer's gene?

The researchers also looked at something called APOE ε4.

APOE is a gene involved in transporting fats around the body, and one particular version – APOE ε4 – is associated with an increased risk of developing Alzheimer's disease.

Interestingly, the association between HRT and reduced dementia risk appeared somewhat stronger among women carrying APOE ε4.

Women who had experienced less natural oestrogen exposure over their lifetime also appeared to show a greater association.

This is one reason the researchers believe the future of HRT may become increasingly personalised.

Rather than simply asking:

"Is HRT good or bad?"

the better question may eventually become:

"Which type of HRT is appropriate for which woman, at what age, and for how long?"

That's a much more complicated question – but probably a much more useful one.

So does HRT prevent dementia?

This is the really important bit.

We don't know.

This was an observational study.

Researchers looked at what happened to women who had and hadn't used HRT. They didn't randomly assign women to take HRT or a placebo and then follow them for decades.

That distinction matters.

Women who use HRT may differ from women who don't in lots of other ways.

They may have different levels of education, income, healthcare access, exercise, diet or other lifestyle factors that could also influence dementia risk.

Researchers can adjust statistically for many of these differences, but they can't necessarily eliminate all of them.

So the study can tell us:

HRT use was associated with a lower risk of dementia.

It cannot tell us:

HRT caused the reduction in dementia risk.

That's an important difference.

We also don't know which HRT might matter

There's another limitation that's particularly relevant to women taking HRT today.

The UK Biobank data didn't contain enough detailed information for researchers to properly compare different:

• types of oestrogen

• types of progestogen

• doses

• tablets

• patches or gels

• vaginal oestrogen

• testosterone

That's a pretty big missing piece.

Modern HRT prescribing can look very different from the HRT women were taking decades ago.

Someone using transdermal oestrogen through a patch alongside micronised progesterone isn't necessarily having the same treatment as someone who previously took an older oral combined HRT preparation.

The researchers themselves say future studies need to examine the composition, dose and method of delivering HRT.

Should I take HRT to prevent dementia?

At the moment, HRT isn't recommended specifically as a treatment to prevent dementia.

HRT is primarily prescribed to manage menopause symptoms and, in some circumstances, help protect bone health.

Whether it's suitable for you depends on your symptoms, age, medical history and individual risk factors.

The latest findings are certainly encouraging – particularly for some groups of women – but they aren't a reason to start HRT purely because you're frightened of developing dementia.

That's a conversation to have with your GP or menopause healthcare professional.

What if I can't – or don't want to – take HRT?

This research absolutely does not mean that women who don't take HRT are destined to develop dementia.

Far from it.

There are plenty of things we already know are associated with maintaining brain health as we age.

Looking after your cardiovascular health is particularly important because what's good for your heart tends to be good for your brain too.

That includes:

• keeping physically active

• not smoking

• keeping blood pressure under control

• managing cholesterol

• treating diabetes

• limiting excessive alcohol

• staying socially connected

• keeping mentally active

• looking after your hearing

None of those are quite as exciting as discovering a magic anti-dementia pill.

But they're things we can actually do something about.

And what about menopause brain fog?

This research may understandably make anyone currently forgetting words, appointments and why they opened the fridge feel slightly nervous.

But menopause brain fog isn't the same thing as dementia.

Memory and concentration difficulties are common during perimenopause.

And there can be several things happening at once.

If you're waking up four times a night drenched in sweat, exhausted the following morning, anxious and trying to juggle work, children, ageing parents and approximately 84 things on your mental to-do list, it's hardly surprising if your brain occasionally refuses to supply the word colander.

Persistent or worsening memory problems should always be discussed with your GP, particularly if they're affecting everyday life.

But occasionally forgetting why you walked into a room during perimenopause isn't evidence that you're developing Alzheimer's.

The Hot Again take

For years, the conversation around HRT has often been reduced to:

HRT = good

or

HRT = bad.

Women's bodies are rather more complicated than that.

This study suggests that HRT use may be associated with a lower risk of dementia, particularly when started around the usual menopause years and among certain groups of women.

That's encouraging.

It's also not proof that HRT prevents Alzheimer's.

What it does show is why we desperately need more research into menopause and women's brain health – and why future HRT advice may become much more personalised than it is today.

For now, the decision about whether to take HRT should still be based on your symptoms, your medical history, your individual risks and benefits, and a conversation with a healthcare professional.

But it's reassuring to see researchers finally asking bigger questions about menopause.

Because getting us through the hot flushes is important.

Looking after our health for the next 30 or 40 years matters too.

This article is for general information only and isn't medical advice. HRT isn't suitable for everyone. If you're considering starting, stopping or changing HRT, speak to your GP or another appropriately qualified healthcare professional.